Continuously operating mixing and kneading machine

ABSTRACT

Continuously operating mixing and kneading machine embodying a continuous, rotating, reciprocating worm shaft mounted in a housing, which machine is divided into a feeder zone with continuous worm channels; an initial pressure buildup zone with discontinuous worm channels and with kneading dogs additionally mounted in the housing; a detensioning zone and a reintroduction zone, both with continuous worm channels; and a second pressure buildup zone with discontinuous worm channels and with kneading dogs mounted additionally in the housing.

United States Patent inventors Erwin Ruettener Riehen; Fritz Sutter,Pratteln, both of, Switzerland Appl. No. 776,418 Filed Not/.48, 1968Patented Aug. 24, 1971 Assignee Buss AG.

Basel, Switzerland Priority Nov. 20, 1967 Switzerland 16,330/67CONTINUOUSLY OPERATING MIXING AND KNEADING MACHINE 2 Claims, 4 DrawingFigs.

US. Cl 259/5, 259/9 Int. Cl B0" 7/02, BOlf 13/04 Field oi'Search259/4-10, 21,40,109, 110

,L H q 22 [56] References Cited UNITED STATES PATENTS 2,731,247 1/1956Hudry 1. 259/6 3,031,030 4/1962 Rodenacker. 259/9 UX 3,219,320 11/1965Sutter 259/5 3,224,739 12/1965 Schuur 259/4 3,346,242 10/1967 List 259/5X 3,347,528 10/1967 List et al.... 259/10X 3,367,635 2/1968 Gresch 259/4Primary Examiner-James Kee Chi Attorney-Abraham A. Saffitz PATENTEDM1824 um SHEET 1 0F 3 INVENTORS:

Erwin RUETTENER and Fritz By M0441) s TTEB 32 mg l x INVENTORS: a: ErwinRUETTENER and Fritz SUTTER L yflulaw 41% ATTORN PATENTEU AUG24I97|3.601. 370

sum 3 or 3 INVENTORS:

Erwin RUETTENER and Fritz S TTE By W l- ATTORN product is to beprocessed into granules, calendered or otherwise further treatedfollowing this process,it is essential that any components present insolution in the product in the fonn of vaporior gas should be releasedfrom it and extracted, if the end-product is to meet high standards ofquality, as is the case r for instance with plastics for gramophonerecord manufacture or for electrical insulators. v

In ,what manner such products for release, hereinafter referred to as.gases, penetrated into the product is not of significance to thepresent problemDifficulties in extracting the gases from the productarise from the viscosity and elasticity of the latter. These propertiesobstruct the passage of the gases tojthe surface, the only situation inwhich the bubbles of gas can burst and release the gas.

One possible method of effecting this would be to increase thetemperature so as to reduce the viscosity of the product, thusfacilitating the passage of the gas bubbles to the surface.

This is often impossible, however, as certain products would nottolerate an adequately large rise in temperature.

A second method of liberating the gas consists in subjecting the productto an abrupt drop in pressure, using a choke ring. As the productemerges in a thin layer between the choke ring and the shaft, it doesindeed display an extended surface area with consequent facilitation ofdegassing, but if by reason of its elasticity or internal viscosity thisthin layer immediately contracts again to form rolls with a reducedsurface area, it is difficult to extract the gas. 1

A further difficulty then arises in bringing these rolls back into thespiral channels of the worm. beforev they have remained so long in thedegassing zone that they choke the latter or cause damage to theproduct, for example by reason of a protracted temperature effect.

The mixing and kneading machine now suggested not only I eliminatesthese disadvantages but additionally permits more effective degassingthan is possibleby decompression of the product alone.

The proposed mixing and kneading machine, which embodies a continuous,rotating, reciprocating worm shaft mounted in a housing, ischaracterized by the fact that it is divided into a feeder zone withcontinuous worm channels; an initial pressure buildup zone withdiscontinuous worm channels and with kneading dogs additionally mountedin the housing; a detensioning and a reintroduction zone, both withcontinuous worm channels; and a second pressure buildup zone withdiscontinuous worm channels and with kneading dogs additionally mountedin the housing. One example of the execution of the subject of theinvention is illustrated in the accompanying drawings, in which:

FIG. 1 shows a vertical longitudinal section of the mixing and kneadingmachine FIG. '2 shows a top view, partially in section, of the mixingand kneading machine FIG. 3 shows a view, partially in section, of thedetensioning and reintroduction zone less shaft and FIG. 3a shows across section along the line A-A in FIG. 3.

A worm shaft 3 is borne in a housing 4 and is driven by a power unit notshown in detail, in such manner that it rotates and at the same timeexecutes a reciprocating axial movement and in the manner as shown in[1.8. Pat. No. 3,367,635 to W.

' Gresch, dated Feb. 6, 1968.

closure of the degassing well being formed by. an inspectio glass 7 withan airtight fit.

2 The worm shaft 3 which extends throughout the entire housing 4is-provided with continuous worm channels 13 over the length of thefeeder zone 8. Over the length of the first pressure buildup zone 9, theworm channels 14 on the shaft 3 are discontinuous, but additionalkneading dogs 15 are mounted in the housing (FIG. 3). The end of thefirst pressure buildup mine is formed by a choke ring 16 mounted in thehousing 4 and effecting a conical contraction oflthehousing diameter.

Over the length of the detensioning zone 10 the reintroduction zone 11,the shaft 3 is again provided with comma: ous worm-channels 17, while inthe second pressure buildup}; zone 12 it is again provided withcontinuous worm channels 18. In this second pressure buildup zone 12,too, the interior wall of the housing carries kneading dogs 19.

At the exit from the second pressure buildup zone 12 is a flange-mounteddischarge worm '20 in which if appropriate an additional degassingprocess within a degassing well 21 and a vacuum feed pipe 22 can takeplace.

Within the reintroduction zone 11 a cutaway portion of the interior wallof the housing takes the shape of a segment of a circular cylinder innerlining, the axis of the said circular cylinder being angled in relationto the worm shaft 3 in the direction of the degassing well 5. Thesegment edge thus formed is rounded off to the interior wall of thedegassing well 5 with a radius tapering ofi in the direction of rotationof the shaft 3 to zero.

The product for processing, in the form of powder, chips or granules ora mixture thereof, enters the feeder zone8 of the mixing and kneadingmachine by way of the infeed device 1 and the infeed opening 2.

The continuous worm channels 13 of the shaft 3 in the sector of thisinfeed zone 8 feed the product continuously and without intermediatehalt into the first pressure buildup zone 9, where it is mixed andkneaded intensively and brought to high pressure. In this process thespecific volume of the product is reduced. Account may be taken of thisby filling out the interstices in the discontinuous worm channels 14with channel occlusion elements 23. Thereafter the product proceeds intothe area of the choke ring 16 and flows in a thin layer between thelatter and the well 3 through into the detensioning zone 10. As a resultof this the pressure sinks abruptly, thus releasing the components ingaseous form dissolved in the product, allowing them to rise up thedegassing shaft and be drawn off into the vacuum feed pipe 6. However,the viscosity of the product pennits only a portion of the gas to escapefrom it. 1 The continuous worm channels 17 along the detensioning zone10 feed the product onward without a halt through the reintroductionzone 11 and into the second pressure buildup zone 12.

This zone 12 is similarly arranged to the initial pressure buildup zone.9, and here again the shaft is provided with continuous worm channels18 and the interior wall of the housing with kneading dogs 19.

Close to the intake zone 11, the zone 12 is not completely filled outwith the product. In this zone the product is repeatedly torn apart andpressed together again. This results in a very large product surfacearea which permits a correspondingly powerful additional extraction ofgas. The gas as it emerges is able to stream back through the gapsbetween the product and the worm channels 18 into the degassing shaft 5,against the direction of feed. The compound movement of the shaft 3 madeup of a rotating movement and an axial reciprocating movementconsiderably facilitates this retrograde gas stream and the layout ofthe intake zone 11 described ensures that the entire flow of product istransferred and no congestion arises in the degassing shaft 5. It ispossible to supervise the proper functioning of the reintroduction zonethrough the inspection glass.

As the product is fed onward through the second pressure buildup zone12, the gaps in the product close up, it is again compressed and leavesthe machine in a gently pulsating stream. In the flange-mounteddischarge worm 20 directly following, which moves only in rotation, thepressure is completely equalized. At the transition point to thedischarge wonn 20, where'the product is again tornapart andrecompressed; it ispossible to carry out further degassing by means ofthe degassing pipe 21 and the vacuum feed pipe 22.

Using the device proposed and a viscous thermoplastic not behaving inaccordance with Newtons principles of internal friction when in aplastic rhelogical condition, it has been found possible to operate theexpulsion of volatile components with infinite variability within arange of ZOO-1,000 kg. per hour without any disadvantages appearing. Thematerial in the form of a powder with a low bulk weight was placed inthe feeder hopper of a single-spindle continuous mixing and kneadingmachine with a reciprocating shaft and was brought to a condition ofmolten viscous plasticity by the application of heat and kneading,compressed under ascending pressure, detensioned and purged of volatilecomponents, reintroduced into the worm by means of the proposed deviceand the pressure simultaneously built up again.

What we claim is:

. l. A continuously operating mixing and kneading machine comprising:

1. a rotating and reciprocating worm shaft 2. a housing surrounding saidshaft provided with a feeder opening, a degassing well adapted forattachment .to vacuum means,

3. a feeder zone belowsaid'feeder opening in said housing provided withcontinuous wormchannels, I I

4. an initial pressure buildup zone formed by discontifl 'ous wormchannels on said shaft and kneading dogs attached and mounted to theinner wall of said housing to build up the mixing pressure from saidfeeder zone,

5.v a detensioning zone formed by continuous worm'channels on said shaftwhich follows the pressure buildup and releases the pressure buildup, g

. a reintroduction zone fonnedby continuous worm channels on said shaftfollowing said detensioning zone ,.said reintroduction zone being formedwith a cut away portion of the interior wall of said housing in the formof asegment of a circular cylinder having an axis thereof which is at anangle inrelation to the worm shaft and lies in the direction'of saiddegassing well,- the edge of said segment facing the/interior wall ofthe degassing well being.

rounded off with. a radius tapering ofi in the direction of rotation ofthe shaft of zero and 7. a second pressure buildup zone formed bydiscontinuous worm channels on said shaft and kneading dogs mountedwithin the housing. V

2. A machine as claimed in claim 1 including channel occlusionelementswhich are rotatably moveable in and through the discontinuousworm channels to aid in compacting and reducing the volume of themixture being kneaded.

1. A continuously operating mixing and kneading machine comprising:
 1. arotating and reciprocating worm shaft,
 2. a housing surrounding saidshaft provided with a feeder opening, a degassing well adapted forattachment to vacuum means,
 3. a feeder zone below said feeder openingin said housing provided with continuous worm channels,
 4. an initialpressure buildup zone formed by discontinuous worm channels on saidshaft and kneading dogs attached and mounted to the inner wall of saidhousing to build up the mixing pressure from said feeder zone,
 5. adetensioning zone formed by continuous worm channels on said shaft whichfollows the pressure buildup and releases the pressure buildup,
 6. areintroduction zone formed by continuous worm channels on said shaftfollowing said detensioning zone, said reintroduction zone being formedwith a cut away portion of the interior wall of said housing in the formof a segment of a circular cylinder having an axis thereof which is atan angle in relation to the worm shaft and lies in the direction of saiddegassing well, the edge of said segment facing the interior wall of thedegassing well being rounded off with a radius tapering off in thedirection of rotation of the shaft of zero and
 7. a second pressurebuildup zone formed by discontinuous worm channels on said shaft andkneading dogs mounted within the housing.
 2. a housing surrounding saidshaft provided with a feeder opening, a degassing well adapted forattachment to vacuum means,
 2. A machine as claimed in claim 1 includingchannel occlusion elements which are rotatably moveable in And throughthe discontinuous worm channels to aid in compacting and reducing thevolume of the mixture being kneaded.
 3. a feeder zone below said feederopening in said housing provided with continuous worm channels,
 4. aninitial pressure buildup zone formed by discontinuous worm channels onsaid shaft and kneading dogs attached and mounted to the inner wall ofsaid housing to build up the mixing pressure from said feeder zone,
 5. adetensioning zone formed by continuous worm channels on said shaft whichfollows the pressure buildup and releases the pressure buildup,
 6. areintroduction zone formed by continuous worm channels on said shaftfollowing said detensioning zone, said reintroduction zone being formedwith a cut away portion of the interior wall of said housing in the formof a segment of a circular cylinder having an axis thereof which is atan angle in relation to the worm shaft and lies in the direction of saiddegassing well, the edge of said segment facing the interior wall of thedegassing well being rounded off with a radius tapering off in thedirection of rotation of the shaft of zero and
 7. a second pressurebuildup zone formed by discontinuous worm channels on said shaft andkneading dogs mounted within the housing.